AMR-to-Text Generation via GF Normunds Grūzītis University of Latvia, Institute of Mathematics and Computer Science National information agency LETA GF Summer School 2017, Rīga, Latvia This work has received funding in part from the Latvian State research programs SOPHIS and NexIT, the EU Horizon 2020 project SUMMA (grant No. 688139), and the European Regional Development Fund (grant No. 1.1.1.1/16/A/219).
Agenda • Frame semantics – FrameNet – PropBank • AMR • Text-to-AMR parsing, AMR-to-text generation – SemEval 2016 – SemEval 2017
Semantic Role Labelling (SRL) FrameNet TurboParser + SEMAFOR: http://demo.ark.cs.cmu.edu/parse PropBank LTH parser: http://barbar.cs.lth.se:8081/
FrameNet (https://framenet.icsi.berkeley.edu)
FrameNet (https://framenet.icsi.berkeley.edu)
FrameNet (FN) • A lexico-semantic resource based on the theory of frame semantics (Fillmore et al. 2003) – A semantic frame represents a cognitive, prototypical situation (scenario) characterized by frame elements ( FE ) – semantic valence – Frames are “evoked” in sentences by target words – lexical units ( LU ) – FEs are mapped based on the syntactic valence of the LU • The syntactic valence patterns are derived from FN-annotated corpora (for an increasing number of languages, incl. Latvian) – FEs are split into core and non-core ones • Core FEs uniquely characterize the frame and syntactically tend to correspond to verb arguments • Non-core FEs are not specific to the frame and typically are adjuncts
Berkeley FrameNet as Interlingua Introduced in BFN , reused in SweFN want .v..6412 känna_för .vb..1 Some valence patterns found in SweFN Some valence patterns found in BFN e.g. “[ I ] Experiencer do n't WANT [ to deceive anyone ] Event ” e.g. “[ Jag ] Experiencer KÄNNER FÖR [ en tur på | landet ] Focal_participant ” an embedded frame
FrameNet and GF Existing FNs are not entirely formal and computational • – A limited but computational FN- based GF grammar and lexicon Grammatical Framework: • – Separates between an abstract syntax and concrete syntaxes – Provides a general-purpose resource grammar library (RGL) The language-independent layer of FrameNet (frames and FEs) – • the abstract syntax – The language-specific layers (surface realization of frames and FEs; LUs) – concrete syntaxes RGL can be used for unifying the syntactic types used in different • FNs and for the concrete implementation of frames – FrameNet allows for abstracting over RGL
Use case (1) Provide a semantic API on top of RGL to facilitate the development • of GF application grammars – In combination with the syntactic API of RGL – Hiding the comparatively complex construction of verb phrases mkCl person ( mkVP ( mkVP live_V ) ( mkAdv in_Prep place )) -- mkCl : NP -> VP -> Cl -- mkVP : V -> VP -- mkVP : VP -> Adv -> VP -- mkAdv : Prep -> NP -> Adv Residence -- Residence : NP -> Adv -> V -> Cl person -- NP (Resident) ( mkAdv in_Prep place ) -- Adv (Location) live_V_Residence -- V (LU)
Use case (2) FN-annotated knowledge bases à multilingual verbalization • Imants Ziedonis ir dzimis 1933. gada 3. maijā Slokas pagastā. Imants Ziedonis was born in Sloka parish on 3 May 1933.
FrameNet-based grammar: abstract • Frame valence patterns are represented by functions – Taking one or more core FEs (A-Z) and one LU as arguments – Returning an object of type Clause whose linearization type is {np: NP; vp: VP} fun Desiring_V : Experiencer_NP -> Focal_participant_Adv -> V -> Clause fun Desiring_V2 : Experiencer_NP -> Focal_participant_NP -> V2 -> Clause fun Desiring_V2_Pass : Experiencer_NP -> Focal_participant_NP -> V2 -> Clause fun Desiring_VV : Event_VP -> Experiencer_NP -> VV -> Clause • FE s are declared as semantic categories subcategorized by the syntactic RGL types – NP , VP , Adv (includes prepositional objects), S (embedded sentences), QS cat Event_VP cat Focal_participant_NP cat Experiencer_NP cat Focal_participant_Adv
FrameNet-based grammar: concrete The mapping from the semantic FrameNet types to the syntactic RGL • types is shared for all languages – Linearization types are of type Maybe to allow for optional (empty) FEs lincat Focal_participant_NP = Maybe NP lincat Focal_participant_Adv = Maybe Adv To implement the frame functions, RGL constructors are applied to the • arguments depending on their types and syntactic roles, and the voice lin Desiring_V2 experiencer focal_participant v2 = { np = fromMaybe NP experiencer ; vp = mkVP v2 (fromMaybe NP focal_participant ) } lin Desiring_V2_Pass experiencer focal_participant v2 = { np = fromMaybe NP focal_participant ; vp = mkVP (passiveVP v2 ) (mkAdv by8agent_Prep (fromMaybe NP experiencer )) }
http://grammaticalframework.org/framenet/
Semantic Role Labelling (SRL) FrameNet TurboParser + SEMAFOR: http://demo.ark.cs.cmu.edu/parse PropBank LTH parser: http://barbar.cs.lth.se:8081/
PropBank (http://propbank.github.io)
AMR (Abstract Meaning Representation) • From SRL to whole-sentence meaning representation – Incl. PropBank SRL, NER and NEL, treatment of modality, negation, etc. • Simple and compact data structure – PENMAN notation: directed labeled graph encoded in a tree-like form – Easy to read and write (for a human), and traverse (for a program) – Langkilde and Knight (1998) à Banarescu et al. (2013) • Aimed at large-scale human annotation and semantic parsing – Practical , replicable amount of abstraction – An actual sembank of 40K+ sentences • Captures many aspects of meaning – Aims to abstract away from (English) syntax
AMR (Abstract Meaning Representation) • Nodes are variables labelled by concepts – Entities, events, states, properties – s / soldier : s is an instance of soldier • Edges are semantic relations • AMR abstracts in numerous ways by assigning the same conceptual structure to different surface realizations f / fear-01 pol arity - s / soldier d / die-01 ARG1 (Pust et al., 2015)
AMR (Abstract Meaning Representation) AMR is still biased • towards English or other source languages Meanwhile, AMR is • agnostic about how to derive meanings from strings, and vice versa Xue N., Bojar O., Hajič J., • Palmer M., Uresova Z., Zhang X. Not an Interlingua, but close : Schneider N., Flanigan J., O’Gorman T. Comparison of English AMR Tutorial at NAACL 2015 AMRs to Chinese and https://github.com/nschneid/amr-tutorial/ Czech. LREC 2014
Text-to-AMR : human annotation https://amr.isi.edu/editor.html
AMR-to-text : human evaluation
Sample AMR (1) # ::snt A fourth member, Jean-Marc Rouillan, remains behind bars. (r / remain-01 :ARG1 (p / person :wiki - :name (n / name :op1 "Jean-Marc" :op2 "Rouillan") :mod (p2 / person :ARG0-of (h / have-org-role-91 :ARG2 (m / member)) :ord (o / ordinal-entity :value 4))) :ARG3 (b / behind :op1 (b2 / bar)))
Sample AMR (1) # ::snt A fourth member, Jean-Marc Rouillan, remains behind bars. (r / remain-01 :ARG1 (p / person :wiki - :name (n / name :op1 "Jean-Marc" :op2 "Rouillan") :mod (p2 / person :ARG0-of (h / have-org-role-91 :ARG2 (m / member)) :ord (o / ordinal-entity :value 4))) :ARG3 (b / behind :op1 (b2 / bar))) Remaining members person 4 jean-marc rouillan – behind bar. Jean-Marc Rouillan, that is the 4th member, is remained behind a bar.
Sample AMR (1) # ::snt A fourth member, Jean-Marc Rouillan, remains behind bars. (r / remain-01 :ARG1 (p / person :wiki - :name (n / name :op1 "Jean-Marc" :op2 "Rouillan") :mod (p2 / person :ARG0-of (h / have-org-role-91 :ARG2 (m / member)) :ord (o / ordinal-entity :value 4))) :ARG3 (b / behind :op1 (b2 / bar))) Remaining members person 4 jean-marc rouillan – behind bar. JAMR Jean-Marc Rouillan, that is the 4th member, is remained behind a bar. GF
Sample AMR (1) # ::snt A fourth member, Jean-Marc Rouillan, remains behind bars. (r / remain-01 :ARG1 (p / person :wiki - :name (n / name :op1 "Jean-Marc" :op2 "Rouillan") :mod (p2 / person :ARG0-of (h / have-org-role-91 :ARG2 (m / member)) :ord (o / ordinal-entity :value 4))) :ARG3 (b / behind :op1 (b2 / bar))) Remaining members person 4 jean-marc rouillan – behind bar. JAMR Jean-Marc Rouillan, that is the 4th member, is remained behind a bar. GF
Sample AMR (2) # ::snt They should have been expelled from school at a minimum. (r / recommend-01 :ARG1 (e / expel-01 :ARG1 (t / they) :ARG2 (s / school) :degree (a / at-a-minimum))) Should they at-a-minimum expel school. JAMR It is recommended that they are expelled to a school at a minimum. GF expel-01 ARG0 = PAG (prototypical agent) ARG1 = PPT (prototypical patient) ARG2 = DIR (direction) à DIR_Prep à to_Prep ToDo: based on statistics from PropBank and FrameNet corpora , “reconstruct” Prep-s, depending on frame/verb valency, ARG role, or NP head
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